The 37-year-old right-hander faced 20 batters at Bright House Field in Clearwater, Fla., striking out six.
"[I felt] real, real good," Martinez told The Associated Press. "I didn't feel tired. I felt like I could still do a little bit more. ... I was feeling better as I got going. More confidence. More comfortable on the mound."
Phillies general manager Ruben Amaro Jr., who was on hand to watch Martinez pitch, agreed.
"I thought it went very well," Amaro told the AP. "The ball seemed to be coming out of his hand much better, I think, in the second two innings than the first. I was impressed with his ability to throw his offspeed pitches for strikes."
The Phillies signed Martinez last Wednesday to a prorated $2 million contract that guarantees him about $938,000 for the rest of the season and immediately placed him on the 15-day disabled list. They officially said he has a right shoulder strain, but the move was purely procedural, giving him time to ready for game action.
The club remains tight-lipped on the three-time Cy Young Award winner's schedule. Assistant general manager Scott Proefrock said that how Martinez feels Wednesday will determine whether he next pitches in another simulated game or in an actual game with a Minor League club.
If Martinez's body reacts well, he will likely begin his Minor League rehab Sunday in Florida.
Martinez is eligible to join the Phillies on July 30, but he is expected to need at least three rehab outings, putting him on track to reach the Majors in early August.
That could leave the club with a surplus of starers, a problem that manager Charlie Manuel said he would love to have. Rodrigo Lopez, whom Martinez is seemingly destined to replace, beat the Cubs on Monday and is 2-0 with a 2.60 ERA in three starts.
Martinez should still join the rotation when healthy, but his agent took no chances. The righty's contract contains incentives for relief appearances as well as for starts, days on the active roster, postseason hardware and the Comeback Player of the Year Award.
For now, Marintez is just pleased with how he feels.
"I didn't have a Spring Training and I'm still throwing strikes," he told the AP. "To me, [Tuesday] was a plus."
David Gurian-Peck is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.